<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div class="test">
        <div class="box"></div>
    </div>
</body>
<style lang="less">
    .test{
        display: flex;
        justify-content: center;
        align-items: center;
    }
</style>
</html>